During the summer, in hot countries such as Australia, large amounts of heat from the sun's rays enter houses through their roof tops and heat up the attic space or roof chamber beneath the roof of the house. In some cases the temperature in the roof chamber can rise to up to 70.degree. C. and the temperature inside the house will consequently increase. To address this problem, it is known to install turbine roof ventilators to extract air from roof chambers which work on the well known principle that hot air rises, and which allow hotter air to escape from the roof chamber before the temperature of the air in the roof chamber rises excessively. During the winter, roof ventilators also help keep houses dry, remove shower and kitchen steam, keep insulation dry and thus help prevent mould and mildew growth.
Turbine roof ventilators comprise a rotatable sleeve on the top end of which is mounted a rotatable turbine wheel or hood. The turbine hood includes a closed circular, usually convex upper end which prevents ingress of rain into the sleeve and thus into the roof chamber, a lower ring and a series of arcuate turbine blades extending from the lower ring to the upper end through which hot air flows. The turbine blades can rotate either due to winds or breezes, or due to the flow of air from out under the roof through the turbine.
Although turbine roof ventilators work, several such devices may be required for even quite small roofs.
It is an object of the present invention to provide improvements to turbine roof ventilators which increase their efficiency and usefulness.